Magnetic bearings are often used in devices which have a drive shaft which rotates at high speed, such as a so-called turbo compressor. In magnetic bearings, for ease of designing the position control system, it is desirable that a control current for causing the electromagnets to generate an electromagnetic force and the sum of the electromagnetic forces (also referred to as a “combined electromagnetic force”) of the electromagnets have a linear relationship. There is a commonly used linearization technique in which while a bias current (fixed value) is being previously passed through the coils of the electromagnets, the control current (which varies depending on the position of the drive shaft) is superposed on the bias current, so that the resultant current is passed through the coils (see, for example, PATENT DOCUMENT 1).